The invention relates to needle-free injection systems that employ pressurized gas to deliver injections of injectable fluid.
Needle-free injection systems provide an alternative to standard fluid delivery systems, which typically use a needle adapted to penetrate the outer surface of a target. Typically, needle-free injection systems are designed to eject the fluid from a fluid chamber with sufficient pressure to allow the fluid to penetrate the target to the desired degree. For example, common applications for needle-free injection systems include delivering intradermal, subcutaneous and intramuscular injections into or through a recipient""s skin. For each of these applications, the fluid must be ejected from the system with sufficient pressure to allow the fluid to penetrate the tough exterior dermal layers of the recipient""s skin.
The invention provides an improved needle-free injection device. The injection device includes a user-grippable housing and a syringe assembly movably secured to the housing. The syringe assembly is configured to expel injectable fluid out of a nozzle upon application of pressurized gas to the syringe assembly. The injection device also includes a pressurized gas delivery mechanism disposed within the housing and configured to selectively apply pressurized gas to the syringe assembly. The pressurized gas delivery mechanism is at least partly actuated by pressing the nozzle onto an injection site so that the syringe assembly moves relative to the housing.